TuningBot DTC Database · v4.37.15
Generic (OBD-II) interpretation in the TuningBot DTC database.
The control module detected that the measured Secondary Air Injection System flow was lower than the value expected while operation was commanded.
Powertrain: engine, transmission and driveline systems.
Generic SAE-standard code: same meaning on every make.
Specific fault index within the subsystem.
Secondary Air Injection System Insufficient Flow Bank 1. The control module detected that the measured Secondary Air Injection System flow was lower than the value expected while operation was commanded.
P0491 is a generic OBD-II code: it has the same meaning on every make and model that follows the SAE standard.
If the fault logic lives in the ECU calibration, yes: our DTC Removal file service disables the specific fault entry. Checksum correction is not included: it is a separate, optional service. Not sure whether your case qualifies? Request a free assessment and our engineers will check your ECU file.
Understand the system behind this code: Secondary Air System
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